季节内振荡水汽收支对长江中下游持续性极端降水强度的调控作用OA北大核心CSTPCD

Based on the gridded daily precipitation dataset in China from 1979 to 2019,the extreme precipitation events in eastern China are identified by using an objective method that comprehensively considers the temporal-spatial strength of gathering.Persistent regional extreme precipitation(PREP)events lasting for at least three days in summer are found most frequently in the middle and lower reaches of the Yangtze River(MLRYR).Based on moisture budget theory,the intraseasonal characteristics of daily precipitation and its moisture budget are diagnosed,and the configuration and evolution of the troposphere systems at primary intraseasonal scales are revealed.The daily precipitation intensity and evolution of PREP proved to be consistent with regional atmospheric column moisture convergence.The 10～30 day quasi-biweekly oscillation(QBWO)and 30～90 day Madden-Julian oscillation(MJO)moisture convergence converted from negative phase to positive phase 1～3 days and 7～9 days prior to the event.The QBWO-related(MJO-related)moisture transport on the region's southern and northern boundary changed from outward to inward 2～4 days(9～10 days)prior to the event.The QBWO-related convection in the South China Sea propagated northward to the MLRYR,prompting corresponding anticyclonic circulation that originated from the northwest Pacific and was in the lower troposphere to move southwestward.Due to the southwest wind in the northwest,the moisture transport in the southern boundary reached the maximum on the onset date of the event.Ten days before the event,the MJO-related anticyclonic circulation in the lower troposphere appeared in the northwestern Pacific Ocean and moved southwestward,the cyclone system in the MLRYR strengthened,while the MJO-related trough that was in the Bay of Bengal and in the middle troposphere began to deepen.Together,these factors gradually increased the MJO-related moisture inward transport in the southern boundary and maintained it until the end of the event.Overall,the combination of the strong MJO-related moisture inward transport and QBWO-related anticyclonic circulation contributed to the occurrence of PREP in the MLRYR.